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The modeling of cyclic behavior in rock remains a challenge due to complex deformation characteristics. This paper studied the mechanical behaviors of granite samples under uniaxial cyclic loading and unloading through cyclic compression tests and acoustic emission (AE) monitoring. Then, a comprehensive body that consisted of an elastic element, plastic element, and friction element was proposed to describe the stress–strain relationship with respect to cyclic behavior, in which the friction element was connected in parallel with the serial combination of the elastic element and plastic element. Finally, the parameters of the proposed model were calibrated based on the mechanism analysis and backpropagation (BP) neural network. Results show that the behavior during unloading is primarily elastic and is accompanied by the obstruction of friction. During reloading, the behavior changes from elastic to elastic–plastic before and after the Kaiser point. The tangential modulus of the elastic element is dynamic in a linear positive correlation with elastic strain and a linear negative correlation with plastic strain; specifically, the elastic strain controls the variation process of the elastic modulus while the plastic strain determines the lower limit. The constitutive law of the plastic element is expressed by a logistic function, which means that the plastic strain increases in a trend of acceleration–deceleration. The friction element plays a major role in processing the massing effect, and the plastic element is prompted before the historical maximum stress, which reflects the ratcheting effect and Felicity effect. The reliability of the proposed constitutive model is confirmed by the comparison of the simulated stress–strain curves with the experimental curves.

Affected by the excavation, the phenomenon of groundwater level drop around mountain tunnels is widespread, resulting in poor accuracy of the existing water inflow calculation formula derived when the groundwater level is fixed. Based on this, a simplified calculation model of tunnel water inflow is constructed when considering drainage, and the tunnel water inflow is calculated according to the Dupuit assumption and conformal transformation. The law of conservation of fluid mass is used to solve the equivalent water head around the tunnel after drainage, and the Taylor formula is used for degradation analysis, and the rationality of the model construction and the correctness of the formula derivation are verified through the tunnel under construction and numerical simulation. Finally, the sensitivity of the characteristic parameters is studied, the evolution law of the equivalent head is revealed, and the influence mechanism is discussed. The research shows that the error between the calculated value of tunnel water inflow and the field measured value can be reduced from 16.1% to 8.9%, which improves the prediction accuracy of tunnel water inflow to a certain extent.

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